Carbon pile electric regulator



' Patented Dec.-17, 1946 CARBON PILE ELECTRI C REGULATOR.

James H. Johnston, Rldgefield Park, N. J., as

slgnor to Bendix Aviation Corporation, Teterbox-o, N. J a corporation ofDelaware Application April 4, 1944, Serial No. 529,494

The present invention deals with electrical regulators and is concernedprimarily with regulators of the so-called carbon pile type.

At the present time carbon pile regulators have come into widespread usefor such purposes as controlling the voltage of the output of generatorsand lso in the governing of current. All of these carbon pile regulatorsoperate on the prin cip-le of varying the pressure applied to the carbonpile, the range of effective pressure on the pile being the regulatingrange of the regulator.

'Ihere has now come into fairly widespread use a regulator which ischaracterized as including the usual carbon pile, one end of which isrelatively fixed. Operatively associated with the other end to applypressure on the pile, is an armature and this armature is carried by aspring of the leaf type, and the extremities of which engage an abutmentor top surface of an electromagnet.

The force of the electromagnet is rendered effective on the armature. Itis evident that the spring above referred to tends to urge the armaturetowards the pile, while the magnetic force tends to withdraw thearmature from the pile. The difference between these two forces is theregulating force or working force on the pile.

With carbon pile regulators of this type some difiiculty has beenexperienced in obtaining desired regulating effects in that under manyconditions the pile is compressed to such an extent as to cause itsresistance to fall beneath a desired minimum. Thus, if the regulator isemployed as a voltage regulator, this undue decrease in the resistanceof the pile causes the voltage to rise beyond a safe limit. Moreover,with no fixed limit on the extent to which the pile may be compressed,chattering and vibration occurs, which is a highly undesirable factor.

With these conditions in mind, this invention has in view as animportant object, the provision, in an electric regulator of thecharacter aforesaid, of means for limiting movement of the armaturetowards the pile whereby definite assurance is had that the pile willnot be compressed beyond a predetermined safe limit.

More in detail, the invention has as an object the provision, in acarbon pile regulator of the type above noted, 01' limiting means forthe armature which is adjustable in nature, so that the extent to whichthe pile may be compressed may be varied as desired.

In carrying out this idea in a practical embodiment, the core 01' theelectromagnet is provided with a bore extending axially thereof. Extend-8 Claims. (Cl. 201 51) ing through this bore and freely movable therein,is a rod, one extremity of which is anchored to the armature, while theother extremity carries some adjustable form of stop, such as a nut,which engages the core. It is evident that with such an arrangement,movement of the armature towards the pile is definitely limited and thelimit may be adjusted by adjusting the nut.

In conditionsof actual use, it has been found desirable to make the stopwhich limits the movement of the armature of a yieldable nature, as suchan arrangement tends particularly to prolong the life of the carbonpile. Accordingly, a further object is the provision, in a carbon pileregulator of the character above set forth, of yieldable means forlimiting movement of the armature towards the pile.

This end is achieved by incorporating in the mechanism above describedan expansion spring. which is disposed about the rod and interposedbetween the end of the core and the nut. The force of this springopposes the force of the leaf spring carrying the armature and itseffect is to provide a yielding stop for the armature.

Various other more detailed objects of the in- I vention such as arisein carrying out the above noted thoughts in a practical embodiment willin part become apparent and in part be hereinafter stated as thedescription of the invention proa leaf spring, the extremities of whichengage the top of the electromagnet. The position of this armaturedetermines the pressure on the carbon pile. The core is formed with abore through which extends a rod, one end of which is anchored to thearmature, and the other end of which carries a stop in the form of a nutwhich engages the end of the core. In a modified form a coiled expansionspring may be interposed between the core and the nut.

For a full and more complete understanding of the invention, referencemay be had to the following description and accompanying drawing,wherein:

Fig. 1 is asection through those parts of a carbon pile regulator withwhich this invention is immediately concerned; and

Fig. 2 is a. similar sectional view of a modii'lcation.

Referring now to the drawing, wherein like reference charactersdenote-corresponding parts,

aei'aeii and first more particularly to Fig. 1, an electromagnet isreferred to in its entirety by the reference character E. Thiselectromagnet comprises tral opening which is preferably conical inshape,

as illustrated, and which is designated l6.

Substantially oppositeto the opening l l'and coaxial therewith, thebottom it is formed with a threaded opening 95. Screwed into thethreaded opening i is a core it, the upper extremity of which extendsinto the opening i l. The core i6 is provided with a bore H! whichextends therethroughout. Assembled within the cylindrical coil spring 29is disposed about the rod 25 and wall It and between the bottom and topwalls ti and i2 is the usual solenoid winding which is identified by thereference character S.

Carried on the upper face of the top wall l2,

and preferably in engagement with the peripheral flange I3 is anabutment ring IS, the exposed surface of which has a slight taper toprovide the conical formation depicted at it.

An armature is indicated at and is carried by a leaf spring assembly 2!.It will be noted that the springs M are of slightly arched or bowedshape and the free ends of this spring rest against the upper surfaceill of the abutment I8. They also fit within the peripheral flange 13with a reasonably snug fit, so that in the assembled relation thearmature 20 is properly centered with respect to the core HE.

A boss 22 is carried by backing plate 23 which bears against the upperface of the spring assembly 2i. Any appropriate fastening element, suchas the screws shown at 24, may be employed to assemble the plate 23,springs 2| and armature 20, as a unit. The boss 22 engages the lower endof a carbon pile which is designated C.

The carbon pile C and solenoid 8' may be connected into an electricalcircuit in any way to provide the desired regulating efiects. When usedas a voltage regulator for a generator, the pile C will be placed inseries with the shunt field of the generator, while the solenoid S willbe connected in across the generator. Thus, as the voltage across thegenerator varies, so will be voltage in the solenoid S. Y

The intensity of the magnetic field of the electromagnet E is therebycaused to vary with the voltage, and will be effective to in turn varythe position of the armature 20. It is evident that as the armature 20applies more pressure to the carbon pile C, its resistance decreases,which in turn makes the field stronger and thus causes the voltage'torise. To prevent this voltage rise nature.

from exceeding a safe limit, the stop now to be described is provided. 7h A rod 25 is threaded at each end. One end of this rod is screwed intoa complemcntal threaded socket in the armature 20, as indicated at 28. r

This anchors this end of the rod to the armature. The other end of therod '25 carries a nut 2'! which engages the end of the core I6.

.This nut 21 may be accompanied by a lock nut 28, so that when anadjusted position is once set, it will be maintained.

With this arrangement it is evident that the armature 20 can movetowards the pile C only up to the point where the nut 21 engages thecore, any further movement being positively inhibited by thestoparrangement. Thus, the voltage may be prevented from rising beyond apredetermined safe limit.

With this arrangement all of the desired regulating effects of thecarbon pile regulator are maintained, but at the same time theseregulating efiects are rendered more stable and all chattering issubstantially eliminated. It is evi interposed between the nut 21 andthe core H6.

The force of this spring 29' opposes that of the spring assembly 2!. Itis evident that the armature 26 may move towardsthe pile C, but thismovement is resisted by the spring 29 in addition to the magnetic force.As the armature moves further awayfrom the core, the magnetic forcedecreases in strength but the resistance of the spring 29 becomesprogressively greater. It is evident that the movement of the armatureis limited, although not in so positive a Moreover, the presence of thespring 29 exhibits a definite tendency to dampen vibrations on the partof the armature.

While two preferred embodiments of the invention are hereinbefore setforth, it is to be clearly understood that the invention is not to belimited to the exact construction illustrated ture for compressing saidpile, and an electromagnet, the improvement consisting of stop means forlimiting movement of said armature towards said pile, said stop meansbeing so arranged as to limit the compression of said pile to apermissible value substantially less than its maximum value and apermissible value such as to prevent a decrease in the resistance of thepile to below a predetermined safe value.

2. In an electric regulator including a carbon pile, an armature havingmeans engaging one end of said pile to apply pressure thereon, a springcarrying said armature, said spring being arranged so as to compresssaid pile, an electromagnet supporting said spring, and a core fixedlymounted as a part of said electromagnet; the improvement comprising stopmeans carried by said armature and arranged so as to be engageable bysaid fixedly mounted core to limit movement of said armature towardssaid pile and the maximum extent of compression of the pile by saidspring to a value suflicient to prevent a decrease in the resistance ofthe pile below a predetermined safe value.

, 3. In an electric regulator including a carbon armature, and a stopcarried by the other end of said rod for engaging said core so as tolimit the maximum extent of compression of the pile by and a coreincluded as a part of said electromagnet, said core being formed with abore, a rod freely movable in said bore and having one'end anchored tosaid armature, the otherend of said rod being threaded and a nut carriedon said threaded end and forming a stop adapted to engage said core todetermine the limit of movement of said armature towards said pile, saidnut being arranged so as to be adjustable exteriorly of said regulatorfor increasing and decreasing the initial pressure applied to said pileby said spring so as to vary the maximum permissible compression'of saidpile.

5. In an electric regulator including a carbon pile, an armature, aspring carried by said armature for biasing the armature so as tocompress said pile, and an electromagnet, said first mentioned springopposing movement of said armature toward said electromagnet; theimprovement comprising an additional yieldable spring means operablyconnected intermediate said electromagnet and armature so as to opposemovement of said armature towards said pile and arranged so as to limitthe compression of said pile by said first mentioned spring to a valuesubstantially less than its maximum and a limited value sufiicient toprevent a decrease in the resistance of the pile below a predeterminedsafe value.

6. In an electric regulator including a carbon pile, an armature havingmeans engaging one end of said pile to apply pressure thereon, a springcarrying said armature, an electromagnet supporting said spring, and acore fixedly mounted as a part of said electromagnet, and spring meansoperably connected to said armature and bearing upon said core foryieldably opposing movement of said armature towards said pile andlimiting the maximum compression of said pile to within a-predeterminedsafe operating range.

'7. In an electric regulator including a carbon pile, an armature havingmeans engaging one end of said pile to apply pressure thereon, a springcarrying said armature, an electromagnet supporting said spring, and acore included as a part of said electromagnet, said core being formedwith a bore, a rod freely movable in said bore and having one endanchored to said armature, a stop carried by the other end of said rod,an expansion spring associated with said rod and positioned between saidstop and said core so as to bias said armature in a direction tending towithdraw said armature from said pile, and the stop and expansion springon the other end of said rod for limiting the maximum compression ofsaid pile to within a predetermined safe operating range.

8. In an electric regulator including a carbon pile, an armature havingmeansengaging one end of said pile to apply pressure thereon, a springcarrying said armature, an electromagnet supporting said spring, and act e included as a part of said electromagnet, said core being formedwith a bore, a rod freely movable in said bore and having one endanchored to said armature, a nut threaded on the other end of said rodand forming a stop for limiting movement of said armature in a pilecompressing direction, and a coil expansion spring disposed about saidrod and interposed between said core and nut and tending to opposemovement of said armature in a pile compressing direction so as to limitthe maximum compression of said pile to within a predetermined safeoperating range.

JAMES H. JOHNSTON.

